Hi Nicolas,
Well, I've tested it on a fresh clean J3 install, adding two products to a fresh clean Hikashop instal (no customization or coding added) and, with no Error reporting (in J3 global config) set on default level and that's what I get - the 500 error.
For me isn't that important, since I know that no dup product codes should be added
but I reported it just in case you've missed something. Anyway, if it's working fine on your side, that's great as long as you don't have any reports 
Thanks again Nicolas
Cheers